Field of the Invention
The invention relates to implants for replacing at least part of a vertebra, for example after ablation of the vertebra.
The document EP-0 567 424-A1 discloses an implant of this kind comprising an intermediate body and two bearing parts adapted to bear against the vertebral plates of vertebrae adjacent the space left by a vertebra that has been removed. Each bearing part is assembled to one end of the intermediate body by a screw connection so that rotation of each bearing part relative to the body varies the total length of the implant. However, it takes a relatively long time to assemble the various components of the implant. What is more, given the number of parts capable of relative movement, adjusting the length of the implant is relatively complicated and takes a long time, which increases the duration of the surgery. Finally, manufacturing the implant entails defining a large number of accurate surfaces enabling relative movement of the parts. Manufacture is long and costly.
U.S. Pat. No. 5,723,013 relates to an implant for replacing a vertebra that is made up of two implant parts sliding one within the other. The two parts are in mutual contact through teeth enabling the length of the implant to be increased by distraction of the two parts. The length cannot be reduced, however. The length of the implant can be adjusted simply and quickly. However, fine adjustment of the length of the implant is not possible.
An object of the invention is to provide an implant that is quick to install during surgery and that enables fine adjustment of its length.
To achieve the above object, the invention provides an implant for replacing at least part of a vertebra, the implant having two parts adapted to be joined together and enabling a total dimension of the implant to be adjusted, each part having a fixed dimension homologous to the total dimension of the implant, characterized in that the parts form a screw connection with each other.
Accordingly, during surgery, the total dimension of the implant is adjusted by moving only the two parts of the implant relative to each other. Adjustment is therefore simple and fast. Similarly, assembling the mobile parts of the implant before or during the operation is simple and fast. What is more, the number of surfaces enabling relative movement of the parts is reduced. Because the surfaces concerned are very accurate surfaces, fabrication of the implant is easy and its cost is low. The screw connection enables fine adjustment of the length of the implant.
At least one of the parts is advantageously in one piece.
This further reduces the number of parts to be assembled.
At least one of the parts is advantageously in more than one piece.
This facilitates obtaining some shapes of the part concerned.
Each part advantageously has at least one lateral opening and the openings can be superposed to receive a fixing member.
This facilitates superposing the openings, in particular when the two parts are relatively mobile by virtue of a screw connection.
At least one of the openings is advantageously elongate.
The elongate opening is advantageously rectilinear and parallel to a direction of measuring the total dimension of the implant.
One part advantageously has an elongate opening and the other part advantageously has at least one circular opening.
One part is advantageously a female part adapted to receive the other part and including a body and a flange which can be moved relative to the body to immobilize the other part by wedging it.
Accordingly, the wall of at least one of the two parts does not necessarily have to have an orifice to receive a member for fixing the two parts together. The wall of each part can therefore be apertured as much as may be required to show the implant clearly on X-rays and to favor the growth of bone with a view to its osteointegration.
The flange is advantageously mobile by virtue of elastic deformation of the female part.
The flange and the body advantageously each have a conduit to receive a member positioning the flange relative to the body.
The conduits are advantageously parallel to a direction in which the other part is received into the female part.
The flange advantageously comprises an uninterrupted collar.
The collar is advantageously in a plane perpendicular to a direction in which the other part is received into the female part.
At least one of the parts advantageously has a toothed end forming an end of the implant.
Other features and advantages of the invention will become apparent in the course of the following description of two preferred embodiments of the invention, which description is given by way of non-limiting example only. In the accompanying drawings: